Dehorning is considered a routine procedure for dairy calves, writes Gemma Chuck.
It is commonly performed without pain relief – even though it causes extensive tissue damage and is known to cause pain.
There are two major components to the pain caused by dehorning. Firstly, the initial pain caused by dehorning and secondly that caused by inflammation of the wound.
Studies – conducted at Massey University and AgResearch – have shown that the combination of using a local anaesthetic and a non-steroidal anti-inflammatory drug (NSAID) prior to dehorning can eliminate any pain caused by this practice.
Administrating a local anaesthetic and NSAIDs at least 10 minutes prior to dehorning or castration will give ample time for these drugs to take full effect. However, this is impractical – from the stock person’s and the animal’s point of view – because the animal has to be handled twice (once to administer the drugs and secondly to perform the procedure) or restrained for the whole 10 minutes.
Therefore, the aim of the study was to find out if giving pain relief (local anaesthetic and a NSAID) immediately prior to dehorning would still provide effective pain relief for calves.
The calves used in this study were about three months of age and were either handled only or dehorned using a scoop dehorner. Half the calves were dehorned without pain relief, while the others were injected with local anaesthetic just prior to dehorning and then given an NSAID intramuscularly immediately after the procedure was performed.
Blood samples were taken (prior to and up to 72 hours after dehorning) to measure cortisol and acute phase protein concentrations. Cortisol is a common measure of the stress response in animals and acute phase proteins are a measure of tissue damage and inflammation.
Calf behaviour was observed while the calves were in their home pens for up to 180 minutes after the procedures were performed. Finally, body weight was measured before and then 24 hours after handling and dehorning.
Cortisol concentrations increased in dehorned calves for up to six hours after having their horns removed. But, the concentrations were similar among calves that received pain relief at the time of dehorning and calves that were only handled.
Acute phase protein concentrations were higher in calves 24 and 72 hours after dehorning and this response was eliminated in calves given pain relief.
Calves that were dehorned spent more time wagging their tails and less time eating compared to those that received pain relief.
Lastly, calves that were dehorned lost weight during the 24-hours after losing their horns. Whereas the calves that were given pain relief at dehorning did not suffer any loss of body weight.
This study showed that dehorning does cause physiological and behavioural changes in calves indicative of pain. However, this can be mitigated by providing pain relief to the animals when dehorning is carried out.
Mhairi Sutherland is a scientist at AgResearch, NZ.